This is employed, particularly in larger, more complex facilities, to confirm that good design practices have been used. It is best conducted using finished P&IDs. Its objectives are as follows:
• Identify elements whose failure could, through malfunction or human error, endanger operating continuity, employees, or equipment
• Confirm that good design practices have been incorporated, including safety systems, mitigating systems, alarms and shutdowns, etc., to eliminate or reduce the consequences of failure to acceptable levels
• Estimate the potential for alternate failure modes
• Determine whether the consequences of failures constitute an acceptable risk
• Modify (or provide additional) design features or safeguards to reduce consequences to acceptable levels
Design practices review focuses on the active elements of the facility—instruments and controls, pumps and drivers, furnaces, compressors, utility supply systems, etc. These elements are examined in “brainstorming” sessions that consider both historic and unusual equipment and control system failure modes. Techniques of inquiry include the “what if” method and the related, more powerful Hazard and Operability Study Method (see the American Institute of Chemical Engineering (AIChE) “Hazard Evaluation Procedures” and, in this manual subsection, Hazard Assessment). Usually an abbreviated, verbal run-through of these techniques resolves concerns or identifies problem areas for later evaluation.